Toothbrush and Method for Producing It

ABSTRACT

A toothbrush comprises a grip part and a head part carrying a set of bristles. The grip part is connected to the head part via a joint which is associated with a spring element from an elastic plastic material. The spring element is configured froth an at least partial outer cover of the joint. In a preferred embodiment, the cover completely covers the joint and seals it off relative to the surroundings.

The invention concerns a toothbrush with a grip part and a head partcarrying a set of bristles, the grip part being connected to the headpart via a joint that is associated with a spring element from anelastic plastic material. The invention also relates to a method forproducing such a toothbrush.

It has been known for a long time that it is useful to structure thehandle of a toothbrush so elastically that, when the toothbrush is used,the set of bristles can execute a movement relative to the grip sectionheld by the user. In this way, the set of bristles can give way byelastic deformation of the toothbrush when excessive brushing forces areapplied, so that the danger of injuring the oral mucosa and the gums isreduced. It is known that the elastic deformation of the toothbrush canbe achieved in two different structural ways. The handle of thetoothbrush can be a single component made of plastic, which has a lowerelastic modulus in a transitional region between the rear grip sectionand the front head section due to special cross-sectional shaping and/ormaterial combinations and therefore greater deformability.Alternatively, a rear grip part and a front head part of the toothbrushconstitute separate components and can be connectable via a joint. Theinvention concerns a toothbrush of the latter type.

A toothbrush of this type is, for example, known from WO99/39610 Al. Thetoothbrush described therein comprises a grip part that has a J-shapedhook section on its front end nearest the set of bristles. A head partalso has a J-shaped hook section on its rear end, nearest the grip part.The two hook sections hook one under the other, forming a gap, and thegap is filled with an elastic plastic material. In this way, the headpart can swivel relative to the grip part when the toothbrush is used,deforming the elastic plastic material and generating the forces ofreaction necessary to restore the head part.

In prior art, the deformation properties of the head part relative tothe grip part depend largely on the thickness of the plastic materialand therefore on the size of the gap between the head part and the grippart. Because the size of the gap is dependent on the design, it is onlypossible to achieve different deformation properties by using differentelastic plastic materials. This is disadvantageous for production.Furthermore, it has been shown that the known toothbrush has undefinedrigidity perpendicular to the desired direction of movement of the headpart so that the toothbrush may bend away during use.

The object of the invention is to create a toothbrush of the this typewith which defined deformation properties during use can be achieved. Inaddition, a method is to be created by which that toothbrush can beproduced simply and at low cost.

With respect to the toothbrush, the object is inventively solved by thespring element being constituted by at least one outer cover of thejoint, the cover preferably consisting of a thermoplastic elastomer.

The invention is based on the fundamental consideration that the elasticplastic material that constitutes the spring element, instead of beinglocated inside the joint, could be located outside thereof in the formof an at least partial outer cover of the joint. This has the advantageof adapting the design of the joint and its possible movements optimallyto the required deformation movements of the head part relative to thegrip part.

In a preferred embodiment of the invention, the joint is aball-and-socket joint or hinged joint. In the case of a ball-and-socketjoint, a spherical joint body is fitted in a complementarily shapedjoint receptacle with a tight fit, so that the head part can be swiveled360° relative to the grip part in any direction. In the case of a hingedjoint, by contrast, a cylindrical joint body is held in a complementaryjoint receptacle so that swiveling of the head part relative to the grippart is only possible in one direction or one plane. The joint can alsohave yet a different design, for example, as a saddle joint.

The outer cover can easily be applied to the joint and, in particular,be overmolded and determines the deformation properties of the head partrelative to the grip part. The forces of reaction caused duringdeformation of the toothbrush in the elastic plastic material of thecover and therefore the spring constant of the spring element can bedetermined as desired by the design and/or the thickness of the coverand/or by the material properties and, in particular, by the Shorehardness of the plastic material.

If the joint permits movement of the head part relative to the grip partonly in one defined plane, as is the case, for example, for a hingedjoint, it is sufficient if the cover has at least two tendon parts thatare fixed at one end to the grip part and at the other end to the headpart. In particular, precisely two tendon parts should be provided thatare located on opposite sides of the toothbrush in the direction inwhich the head part can deflect.

In an especially preferred embodiment of the invention, the coverencloses the joint completely and seals it off relative to thesurroundings. This ensures sufficient resilience in all directions in ajoint that permits movement of the head part relative to the grip partin multiple planes, for example, a ball-and-socket joint. It is alsopreferable to cover the joint completely for reasons of hygiene becausethis is a reliable way of preventing dirt and/or bacteria from enteringthe joint and accumulating there.

The inventive structure of a toothbrush enables the grip part and thehead part to be produced as separate components or consecutively. Thegrip part and the head part may consist of the same material and, inparticular, of the same plastic. However, in a further embodiment of theinvention, the grip part and the head part consist of differentmaterials. This may have cost advantages because only the head part isplaced in the mouth of the user during use of the toothbrush andtherefore has to satisfy more stringent hygienic requirements than thegrip part. In a preferred embodiment of the invention, the head part ismade of plastic and, in particular, of polypropylene. The grip part mayalso be made of plastic and, in particular, of polystyrene or ABS(acrylonitrile-butadiene-styrene copolymers).

The head part can consist of one component. However, in an alternativeembodiment the head part may also be divided into a first head partsection carrying the set of bristles and a second head part sectionconnected to the grip part via the joint, the first head part sectionand the second head part section being interconnected via a furtherjoint. The further joint may be structured as described above inconnection with the first joint, to which reference is made here toavoid repetition. In particular, a further spring element in the form ofa further, at least partial outer cover is assigned to the furtherjoint, wherein the cover may be made of a thermoplastic elastomer asstated. The further cover can be structured as at least two tendonsections as stated, but preferably the further cover seals off thefurther joint completely relative to the surroundings.

The two head part sections can be made of the same material or also fromdifferent materials, although preferably the same plastic, inparticular, polypropylene is used for both head part sections.

The further joint can be a ball-and-socket joint or a hinged joint.

As for the method, the above task can be solved in different ways. In afirst embodiment of the inventive method, the grip part and the headpart are produced as separate components and then interconnected to formthe joint and, in particular, assembled. Thereupon, the joint isovermolded with an elastic plastic material to form the cover and, inparticular, a thermoplastic elastomer. The grip part and the head partare preferably each formed by a plastic injection-molding and are puttogether and overmolded with the cover using an injection-moldingmachine.

The head part can be produced as a single component but it is alsopossible to produce the head part from two head part sections, whereinto form the head part, a first head part section and a second head partsection are produced independently and then interconnected to form afurther joint, whereupon the further joint to form a further cover is atleast partially overmolded with an elastic and, in particular, elastomerplastic material.

In an alternative embodiment of the method, a first component in theform of the grip part or of the head part is initially produced. Theother component is then molded onto this first component in aninjection-molding machine, i.e. the head part or the grip part, to formthe joint. The materials of the grip part and of the head part are,however, not materially bonded but only connected by positive action,i.e. the head part remains moveable relative to the grip part. The jointis then, at least partially and in particular completely, overmoldedwith an elastic plastic material and, in particular, a thermoplasticelastomer to form the cover.

In a preferred embodiment of this method, the grip part, the head partand the cover are produced in a three-stage injection-molding process ina common mold. After the grip part has been injection-molded in a firststep, the head part is molded onto the grip part in a second step,retaining the relative flexibility. Alternatively, the head part can bemolded in the first step and the grip part can then be molded on in thesecond step. The cover that constitutes the spring element is thenovermolded in the third step.

In all embodiments of the method, the cover should completely surroundthe joint and therefore seal it off relative to the surroundings.

Further characteristics of the method, in particular, the materials usedcan be derived from the above description of the toothbrush.

Further details and characteristics of the invention can be seen fromthe following description of example embodiments with reference to thedrawing. The illustrations show:

FIG. 1 side view of an inventive toothbrush

FIG. 2 a head part as a separate component,

FIG. 3 a grip part as a separate component,

FIG. 4 the head part and the grip part after joining together,

FIG. 5 a toothbrush according to an alternative embodiment and

FIG. 6 a further embodiment of the toothbrush according to FIG. 1.

FIG. 1 shows an inventive toothbrush 10, essentially comprising arod-shaped grip part 13 and a rod-shaped head part 11, which aredisposed one behind the other in the longitudinal direction and areconnected to each other at the ends facing each other to form a joint14, wherein the joint 14 is enclosed according to FIG. 1 by a cover 19to form a spring element 17 and is thus completely sealed-off relativeto the surroundings. A set of bristles 12 is provided in theconventional way on the end of the head part 11 furthest from the grippart 13.

FIG. 2 shows the head part 11 as a single component. Herein it can beseen that a spherical joint body 15 is fashioned at the lower endnearest the grip part 13.

FIG. 3 shows the grip part 13 as a single component, comprising a jointreceptacle 16 on the upper end nearest the head part 11, into which thejoint body 15 of the head part 11 can engage.

The head part 11 is preferably made of plastic and is provided with aset of bristles 12. Independently of this, the grip part 13 is also madeof plastic. These two components are then assembled together byinserting the joint body 15 into the joint receptacle 16, where it ispreferably prevented from falling out again by positive action, inparticular, by latching forces. This condition is illustrated in FIG. 4.If the joint body 15 is a sphere, the head part 14 can be freelyswiveled in all directions relative to the grip part 13.

The joint 14 of the pre-assembled toothbrush shown in FIG. 4 is thencompletely overmolded with the cover 19 made of thermoplastic elastomerin a mold for injection molding. The cover 19 constitutes the springelement 17 which, when the head part 11 is swiveled relative to the grippart 13 as the toothbrush is used, produces forces of reaction andrestoring torques that return the head part 11 to its initial positionrelative to the grip part 13, as soon as the load ceases to be applied.

In the depicted variant of the method, the head part 11 and the grippart 13 were produced independently of each other, then assembledtogether and overmolded with the cover 19 in the region of the joint 14.Alternately, it is also possible to produce just the head part 11 in afirst step and then to mold the grip part 13 in an injection-moldingmachine onto the head part 11 in such a way that the two parts connectby positive action, but can swivel relative to each other. Of course, itis also possible to produce the grip part 13 first and then to mold thehead part 11 onto it.

In a third step, the cover 19 is molded on in the region of the joint14. All three steps can be performed in the same injection-moldingmachine.

In the embodiment described above, the joint 14 is a ball-and-socketjoint, so that the head part 11 can swivel relative to the grip part 13in many different directions. Accordingly, the joint 14 is completelyenclosed by the cover 19 so that the required forces of reaction arealways produced in the cover 19, whatever the direction in which thehead part 11 is swiveled. FIG. 5 depicts a modified embodiment in whichthe joint body 15 of the joint 14 is a cylindrical body that is locatedin a joint receptacle with a complementary shape. In this way, the headpart 11 can only be swiveled relative to the grip part 13 in onepredetermined plane about an axis of rotation A aligned in thelongitudinal direction of the cylindrical joint body 15. In thisembodiment, it is not necessary for the joint 14 to be completelyenclosed by the cover 19, rather the cover 19 has two tendon parts 18 aand 18 b that are disposed on opposite sides of the toothbrush 10. Eachtendon part 18 a, 18 b is attached at one end to the grip part 13 and atthe other and to the head part 11. If the head part 11 is swiveledrelative to the grip part 13 about the axis A, a tensile force isapplied to one of the tendon parts 18 a, 18 b, while a compressive forceis applied to the other tendon part. The tendon parts 18 a and 18 bproduce the forces of reaction that determine the resilient deformationproperties of the head part.

In the embodiment depicted so far, only one joint is provided but in afurther embodiment of the invention it is also possible (see FIG. 6) tomake the toothbrush (10) out of three parts, wherein the three parts arepositioned one behind the other and are connected to a brush handle viatwo joints. The grip part 13 has the structure stated in conjunctionwith the previous embodiment. The head part 11 is divided into an upperfirst head part section 11 a carrying the set of bristles 12 and a lowersecond head part section connected via the joint 14 to the grip part 13in the way stated above. A further joint 20 is formed between the firsthead part section and the second head part section that has thestructure described in conjunction with the joint 14 and is structuredas a ball-and-socket joint in the embodiment shown that is enclosed by afurther outer cover 22 made of an elastomer plastic and is completelysealed off relative to the surroundings. The further cover 22constitutes a further spring element 21 that determines the degree ofadjustment of the upper first head part section 11 a compared to thelower second head part section 11 b when the toothbrush is used.

1-24. (canceled)
 25. A toothbrush, the toothbrush comprising: a grippart; a head part, said head part carrying a set of bristles; a joint,said joint disposed between and connecting said head part and said grippart; and a spring element made from an elastic plastic material, saidspring element having a cover which at least partially surrounds saidjoint.
 26. The toothbrush of claim 25, wherein said cover is made from athermoplastic elastomer.
 27. The toothbrush of claim 25, wherein saidcover is formed by at least two tendon parts that are attached to saidgrip part and said head part.
 28. The toothbrush of claim 27, whereinsaid two tendon parts are located on opposite sides of the toothbrush.29. The toothbrush of claim 25, wherein said cover completely enclosessaid joint and seals it with respect to surroundings.
 30. The toothbrushof claim 25, wherein said grip part and said head part consist ofdifferent materials.
 31. The toothbrush of claim 25, wherein said headpart consists of plastic or of polypropylene.
 32. The toothbrush ofclaim 25, wherein said grip part consists of plastic, polystyrene, orABS (acrylonitrile-butadiene-styrene copolymers).
 33. The toothbrush ofclaim 25, wherein said joint is a ball-and-socket joint.
 34. Thetoothbrush of claim 25, wherein said joint is a hinged joint.
 35. Thetoothbrush of claim 25, wherein said head part is divided into a firsthead part section carrying said set of bristles and a second head partsection connected to said grip part via said joint, wherein said firsthead part section and said second head part section are interconnectedvia a further joint, said further joint having a further spring elementcomprising a further, at least partial, outer cover.
 36. The toothbrushof claim 35, wherein said further cover consists of a thermoplasticelastomer.
 37. The toothbrush of claim 35, wherein said further covercompletely encloses said further joint and seals it with respect tosurroundings.
 38. The toothbrush of claim 35, wherein said further jointis a ball-and-socket joint or a hinged joint.
 39. A method for producinga toothbrush, the method comprising the steps of: a) producing a grippart; b) producing a head part; c) interconnecting the head part and thegrip part to form a joint; and d) at least partially overmolding thejoint with an elastic plastic material to form a cover.
 40. The methodof claim 39, wherein, in step b), a first head part section and a secondhead part section are initially produced independently and areinterconnected to form a further joint, and that further joint is thenat least partially overmolded with an elastic plastic material to form afurther cover.
 41. The method of claim 39, wherein one of the grip partand the head part is initially produced as a first component and another one of said the head part and the grip part is then molded on thefirst component to form the joint, wherein only a positive-actionconnection is thereby provided by the joint.
 42. The method of claim 39,wherein the grip part and the head part are each formed by plasticinjection-molding.
 43. The method of claim 41, wherein the grip part,the head part and the cover are produced in a three-stageinjection-molding process in a common mold.
 44. The method of claim 39,wherein the cover consists of a thermoplastic elastomer.
 45. The methodof claim 39, wherein the cover completely encloses the joint and sealsit off relative to surroundings.
 46. The method of claim 39, wherein thegrip part and the head part consist of different materials.
 47. Themethod of claim 39, wherein the head part consists of plastic and or ofpolypropylene.
 48. The method of claim 39, wherein the grip partconsists of plastic, polystyrene or ABS.